Telephone system



N. H. SAUNDERS k FQ III Aug. l2, 1930.

1 .Tu e e h S. t e e h S 8 6 m T1 B. 0 S1 W mw MMD Lm El Ti. F

@W lll] Il www lll eo No1-"man H. vaut-:ciers:

Aug. l2, 1930.

N. H. SAUNDERS TELEPHONE SYS TEM Filed Dec. 10 1926 Y il@ Ullllll llll Qvfll-... OLE i 8 Sheets-Sheet 2 Aug. 12, 1930. N. H. sAUNDERs 1,772,690

TELEYHONE SYSTEM Filed Dec. l0, 1926 8 Sheets-Sheet 3 mfen al" Norman H.Eaunder's HTH:

Aug. l2, 193). N. H. sAuNDERs TELEPHONE SYSTEM 8 sheets-sheet 4 FiledDec. 10, 1926 Im Norm an H. Saunders MKM@ A Aug. l2, 1930. N. H.sAUNDERs TELEPHONE SYSTEM Filed Deo. 10. 1926 8 Sheets-,Sheet 5 Imrannr' Norman H. Saunders Man-H;

Aug. 12, 1930.

N. H. SAUNDERS TELEPHONE SYSTEM a sheets-sheet s Filed Dec. 10, 1926 1|I||d H .nl rl llll @w11 x urn MT wi m 1 r El# ILFI n Mad Im?? NormanHEam-lder's MAME@ US- 12, 1930. N. H. sAuNDERs 1,772,690

TELEPHONE SYSTEM Filed Dec. 1o, 192s a sheets-sheet 7 'Norman H SaundersAug. 12, 1930. N. H. sAUNDERs TELEPHONE SYSTEM Filed Dec. 10 1926 8Sheets-Sheet 8 Inu'en n Norman HEamder's MHH-:

w l I l W M M .m S S S Q www www Nhw l I u., l..

s. .IM i w3 E n NNN SN N Emma m M l TI w I I 4w-1||lNI| S L@ ma SN m...E oo h Patented Aug. 12, 1930 UNITED STATES PATENT-QFFICE NORMAN 1I.SAUNDERB, 0F HOMEWOOD, ILLINOIS, ASSIGNOB TO RESERVE HOLDING COMPANY, OFCHICAGO, ILLINOIS, A COBPOBATIONOF DELAWARE v'rnnrrnorin SYSTEMApplication led December 10,1926. Serial No. 153,791.

The present invention relates to telephone systems in general, but isconcerned more particularly with the production of a new and improvedapparatus for use in tele- 5 phone systems for supplying service to networks of small telephone exchanges, although many of the new featuresare not confined therto.

One feature of the invention has to do with 1o the production of anarrangement for freeing the central office equipment in an automaticexchange when one subscriber on a local battery party line operates hishand generator to signal another subscriber on the same line.

Other features of the invention have to do with the production of newand improved circuits for connector switches for use in extendingconnections to party lines of the 2o local-battery simplex-dialing type.

Another feature of the invention is concerned with the provision of anew and imv proved code-generating device for generating the codesnecessary -to signal the various party-line subscribers to whichconnnections are extended.

Another feature is directed to the provi-4 sion of a new and improvedtrunk circuit for use `on a trunk line seized by an automatic selectorswitch and extending to an operators position. The trunk circuitautomatically projects ringing current out over the trunk line to signalthe distant operator and cuts off the ringing current when the operatorresponds.

The foregoing and other features of the invention may be understood bestfrom a further perusal of the specification in connecticn with theaccompanying drawings comprising Figs. 1-9.

Referring now to the drawings, Figs. 1-7 show by means of the usualcircuit diagrams a suilicient amount of apparatus in a telephone systemembodying the features of the invention to enable the invention to beunderstood; Fig. 8 is a trunking diagram which shows a telephone network comprising four exchanges interconnected by trunk lines; and Fig. 9shows how Figs. 1-7 should be assembled together.

Considering Fig. 8 in detail, the four exchanges shown are A, B, C, andD. Exl changes A and B are automatic exchanges and each has an ultimatecapacity approaching a thousand lines, there being a single order ofselectors in each oflice. The exchange C is a manual exchange of thecommon-battery type, and two way trunk lines are provided connectingthis exchange with each of the other three exchanges. And ex- 50 changeD is an automatic exchange having a capacity approaching 100 lines, thisexchange being provided with connectors only.

It is assumed that exchanges A and B are located relatively close to oneanother, and that telephone service between these two exchanges ischarged for at the same rate as telephone service local to eitherexchange, there being no extra charge for inter-exchange trunking. It isassumed that ex- 7U changes C and D are more or less remotely situatedfrom exchanges A and B and from each other, and that there is an extracharge for service between either of the exchanges C and D and any otherexchange. And it is 7" assumed that exchange C is of relatively smallsize and that the same operator handles calls local to the exchange Cand also calls involving the exchange C either as a switching point oras an originating point or ter- 8 n unating point for inter-exchangeconnections.

Upon reference to exchange A, it will be noted that the line of thetelephone T1 ter- .minates at the exchange in the lineswitch LS1 85 andalso in the bank of the connector Cl. The selector S1 is one of a numberof selectors for handling calls originated by the lines such as the lineof substation T1. The bank of the selector S1 -is multiplied with the 90banksof the incoming selectors S2 and S3. These selectors have access onthe fifth level to a group of connectors of which the connector C2 isone, and they have access on the sixth level to a group of connectorsrepresented by the connector C1. It is assumed that the line ofsubstation Tl is accessible through the twenty-first set of contacts inthe bank of connector C1, being line number 621.

Referring to exchange B, it will be noted 10 that the layout of thisexchange is the same as that of exchange A, the selector S6 being alocal selector, and selectors S4 and S5 being incoming selectors.Connector C3 is reached from the fifth level of the selectors, andconnector C4 is reached from the sixth level. The line of substation T2is assumed to be reached through the first set of contacts in the secondlevel of the connector C4, being line number 621.

Re arding connections between exchanges A an B, it will be noted thatthere is a twoway trunk line TLB extending between the repeaters R1 andR2. This trunk line is one of a roup provided for extending connectionsetween the two exchanges. This trunk line may be seized at theA-exchange when a selector in the A exchange is operated to the thirdlevel, the repeater R1 being interposed to repeat the dialing impulsesand to provide a holding circuit for the selector and ineswitch involvedin the connection. 1n making a call from exchange A to exchange B, thesubscriber dials the same number that would be dialed by a subscriber inexchange B to obtain the same connection, except that the subscriber inexchangeApreiXesthe digit 3 to operate a selector in exchange A toextend connections to an incoming selector in exchange B. In a similarway, calls originated in exchange B and intended for lines terminatingin exchange A are handled through a trunk line and an incoming selectorsuch as the trunk line TL3 and the selector It will be noted that thetrunk line TLl extends between the trunk circuit TC1 in exchange A andthe jack J2 in exchange B. This trunk line is a two way trunk line, andthe selector S2 in exchange A may be operated over this trunk line whenthe operator in exchange C makes connection through the 'ack J2. Thetrunk line TLl may be seized y a selector in exchange A through thefourth level, whereupon the trunk circuit TC1 applies ringing current tothe trunk line to signal the operator in exchange C. Similarly, thetrunk line TL2 is a two-way trunk line connecting exchanges C and B,terminating at the exchange C in the jack J4 and passing through thetrunk circuit TC2 in exchange B to the fourth level of the selector bankand to selector S5.

The trunk line TL4 extending between exchanges C and D terminates atexchange C in the jack J3, and, when it is seized through this jack, theline switch LS3 in exchange D is operated to extend the connection to anidle connector, such as the connector C5. When this trunk line is seizedin exchange D by a connector, ringing current is projected out over thetrunk line by the connector to signal the operator at exchange C.

Referrin now to Figs. 1-3, it will be noted that these rawings show thecircuits of the equipment necessar to set u `the connections between thetelephone su station T1 of exchange A and substation' T2 of exchange B.This equipment comprises the lineswitch LS1 and the selector S1, Fig. 1,the repeater R1, trunk line TL3, the-repeater R2 and the selector S4,Fig. 2, andthe connector C4, Fig. 3. Since the circuits of the selectorS4 may be the same as the circuits of the selector S1 the selector S4has -been indicated by a dotted rectangle.

It will be noted that Figs. 1, 2, 5, 6, and 7, show apparatus forextending a connection from the substation T1 of exchange A to thesubstation T4, of-exchange D. This apparatus includes the lineswitch LS1and the selector S1, Fig. 1, the trunk circuit TCl and the trunk lineTL1, Fig. 2, the trunk circuit TC3 and the cord circuit CC, Fig. 5, thetrunk circuit TC5, the trunk line TIA, and the lineswitch LSB, Fig. 6,and the connector C5, Fig. 7.

The apparatus shown in Fig. 4 is the relay device for generating theringing codes for operating the ringing relays 1n the connectors tosignal the party line subscribers. Although only the code-generatingdevice in exchange B has been shown, it will be understood that asimilar device is provided for exchan e A and another device is providedfor exc an e D. It will be noted that the ringing-co e conductors shownin Fig. 4 extend to the right-hand edge of the sheet and terminate therein circles labeled 1-10. These circles indicate terminals that are to beconnected to the corresponding bank terminals of the Variouscode-selecting switches of the connectors in exchange B, such as thecode-selecting switch CS4 of the connector C4, Fig.- 3, the bank wiresof the switch CS4 being provided with similar circles to indicate theconnection between the code-selector bank and the ringing-codeconductors. The circles numbered 1-10 associated with the code-selectingswitch CS5 of the connector C5, Fig. 7, indicate that the bank wires ofCS5 are connected in the same way to the ringing-code conductors of theassociated code-generating device (not shown).

Gall from substation T1 to substation T2 A detailed description of theoperation of the apparatus shown will now be given. For this purpose itwill be assumed first that the subscriber at substation T1, Fig. 1,desires to converse with the subscriber at substation T2, Fig. 3. Thecalled line number is 621, and the station number on the called line is5. Consequently the number, if called from another tele hone in exchangeB, is 621-5, the dash being used ahead of the 5 to separate the linenumber from the stations digit. Since, however, the calling subscriberis in exchange A, he must prefix a 3 to the number, which then becomes3-621-5. It is assinned that the numbers of subscribers to the twoexchanges are listed in separate portions of the'directory, and thatgeneral instructions are issued to the subscribers to prefix the digit 3when calling from one exchange to the other.

When the subscriber at substation T1, Fig. 1, removes his receiver, theusual receiver and transmitter circuits are completed at the switchhookcontacts, and, in addition, a circuit is closed at contacts 108 throughthe springs 106 of the calling device 105 to the junction of the coilsof the bridged ringer 104. lVhen this occurs, current from the exchangebattery through the winding of line relay 113 flows through theassociated cutoff-relay spring combination through both line conductors101 and 102 in parallel, being afforded a path to ground at the callingsubstation through the two windingsof the ringer 104 in parallel. Linerelay 113 closes a circuit for the pull-down winding 114 through theusual so-called open-main conductor 122 to battery. The pull-downWinding operates the plunger 4117 and the bridge-cut-of armature 116.The bridgecut-ofi armature 116 op'ens the shunt across the talkingconductors and disconnects relay 113. Relay 113 is slow releasing andremains operated for an interval. The pull-down armature 117 o eratesthe springs 118-121,

Aextending the ine conductors 101 and 102 and the private normalconductor 127 to the corresponding conductors 124, 126, and`125 ofselector S1. Line relay 131 of the selector S1 now energizes through thetwo windings of the impedance 130 and over the two conductors of thecalling line in parallel. Line relay 131 closes a circuit orrelay 132and vertical magnet 137, at the same time disconnecting series relay 133from in shunt of relay 132. Magnet 137 is not operated at this timeowing to the relatively high resistance of relay 132. Series relay 133is of relatively low resistance and magnet 137 will operate whenconnected in series with relay 133. The circuit of magnet 137 is closedmomentarily through relay 133 after the armature of relay 131 hasengaged its front contact and before relay 133 has been removed from itsshunt of relay 132. This interval, however, is of such a short durationthat neither relay 133 nor magnet 137 have time to operate. Relay 132,upon operating, closes a locking circuit for itself at armature 144including magnet 137, and at armature 145 places ground on release trunkconductor 125. This closes a circuit through the bridge-cutofl' andholding winding 115 of the lineswitch. The current flow through thiswinding is sufficient to maintain the bridge-cutofl and pull-downarmatures operated after relay 113 falls back and opens the circuitthrough the pull-down winding 114. The advance of the master switch toanother idle trunk takes place responsive-.to the placin of ground onconductor 125 and is controlle over the branch conductor 123 extendingto the master switch bank.

The calling subscriber may now dial the first digit 3 in the desirednumber, whereupon line relay 131 falls back three times due to the threeinterruptions produced in its circuit at springs 106 of the callingdevice 105 upon the return of the calling device to its normal position.It will be noted that off-normal springs 107 of the calling device 105shunt the coils of the ringer 104 so as to afford a better impulsingcircuit for line relay 131 ofthe selector S1. Each time it falls back,relay 131 places relay 133 in multiple with relay 132. When thls occursthe first time, relay 133 operates in series with magnet 137, and magnet137 operates to raise the wipers of the switch one step. Although'theresistance of relay 133 is so low, relatively, that relay 132l willeventually fall back, when shunted by relay 133, it does not have timeto do so during dialing. When the armature is again attracted magnet 137falls back, but the slow-acting relay 133 remains operated until the endof the digit. Magnet 137 is operated two more times, raising the wipersof the switch three steps in all. Upon the operation of relay 133, acircuit is prepared for stepping relay 134. This circuit is completedthrough the interrupter springsof the rotary magnet 140 and theoff-normal contacts 141 as soon as the first step of the switch has beentaken. Relay 134 thereupon operates and locks itself to release trunkconductor 125 at armature 147, and at armature 148 prepares a circuitfor rotary magnet 140. When relay 133 falls back at the end of thedigit, it shifts thecircuit of relay 134 to the test wiper 154preparatory to the usual testing operation, and at the same timecompletes the circuit of rotary magnet 140. Rotary magnet 140 thereuponoperates and advances the wipers 153-155 one step into engagement withthe first set of bank contacts in the third level. Near the end of itsstroke, magnet 140 opens the circuit of relay 134, whereupon relay 134falls back and opens the rotary magnet circuit. The rotary magnet fallsback and again closes its interrupter contacts.

From this point the operation depends upon whether the trunk lineterminating in the first set of bank contacts is busy or idle. If thistrunk line is idle, relay 135 operates at this time seizing the trunk.If the trunk line is busy, the ground potential encountered by testwiper 154 on the busy test contact'short circuits relay 135 and closes anew circuit through the armature of relay 133, normal, the rotary magnetinterrupter contacts, and the off-normal contacts 141 for stepping relay134. Stepping relay 134 operates again, and again closes the rotarymaglos llO

,grounded release net circuit, whereupon the wipers are advanced anotherstep. l

This alternate operation of relay 134 and magnet 140 continues until anidle trunk line is reached, which trunk line, it will be assumed, is theone comprising conductors 156-158 and extending to the repeater R1, Fig.2. When this trunk line is reached, no ground otential is encountered bytest wiper 154, an relay 135, being no longer short circuited, energizesin a circuit including the trunk conductor 125, eleventh-rotary-stepcontacts 142, the rotarymagnet interrupter contacts, off-normal contacts141, and relay 134. Relay 134 does not operate in this circuit onaccount of the relatively high resistance of relay 135. Upon operating,relay 135 at armature 151 opens n. further point in the test circuit andconnects wiper 154 to the grounded release trunk couductor 125, therebymaking the seized trunk busy immediately to the other selectors havingaccess to it. At armature 150, relay 135 opens the locking branch of therelease relay circuit so as to prevent a further operation of magnet 137and relay 133 and to prevent a premature release magnet operation, andat armatures 149 and 152 disconnects conductors 124 and 126 from thewindings of impedance 130 and line relay 131 and extends them throughwipers 153 and 155 to conductors 156 and 158 leading to the repeater Rl.

Line relay 201 of the repeater R1 now operates over the calling line andthrough the two lefthand repeating-coil windings in parallel. Atarmature 206, relay 201 closes a circuit for release relay 202. Relay`202 operates and closes atl armature 208 a circuit :for relay 203. Atarmature 207, relay 202 places ground on release trunk conductor 157, soas to maintain the lineswitch LS1 and the selector S1 operated after therelease relay 132 of the selector S1 falls back responsive to beingshunted and open-circuited by the line relay 131 when the latter fallsback responsive to the operation of switching relay- As a result of theclosure of the circuit of relay 203 at armature 208, relay 203, atarmatures 209 and 210, disconnects the conductors of the trunk line TL3from the corresponding conductors leading tothe selector S3 and connectsthem to the right-hand repeating-coil windings. A ground potential isthereby placed on conductors of the trunk line TL3 through theright-hand repeatingcoil windings, closing a circuit over the conductorsof the trunk line TL3 and through armatures 209 and 210', normal for theline relay (not shown) of the selector S4. This line rela now operatesand prepares the selector 4 for operation in the manner described inconnection with the selector S1. When the calling subscriber dials thesecextending to the connector C4, Fig. 3. It

will4 be noted that each time relay 201 falls back it opens the circuitof relay 202, but

.relay .202 remains operated throughout the digit on account of the factthat it is placed 1n a clod circuit each time before its energizingcircuit is opened.

In the connector C4, relay 305 operates responsive to the grounding ofconductor 302 by the selector S4 when the latter seizes the trunk line,its circuit including off normal contacts 321. At armature 326, relay305 prepares a locking circuit for itself, and at armature 328 itconnects vertical magnet 325 to the operating conductor 313, at the sametime disconnecting rotary magnet 360. Line relay 306 operates voverconductors 301 and 303 from the ground potential supplied to the trunkline TL3 through armature 204 of the repeater R1, and it closes acircuit for release relay 307 through vertical magnet 325. Uponoperating, release relay 307 places ground on locking conductor 314 atarmature 333; grounds release trunk conductor 302 at armature 332; andat armature 334 closes a locking circuit for itself including operatingconductor 313, armature 328, and vertical magnet 325. i

When the calling subscriber dials the third digit 2 in the desirednumber, two interruptions are produced in the circuit of line relay 306of the connector C4 at the line relay 201 of the repeater Rl, with theresult that relay 306 falls back twice. Each time it falls back, relay306 shunts relay 307 with the series relay 311, bringing about theoperation of vertical magnet 325. By the operation of the verticalmagnet, the, wipers 357--359 are raised o posite the second level ofbank contacts. Series relay 311 energizes upon the first impulse ofcurrent and remains energized until the digit is over. At armature 348,relay 311 completes the locking circuit for relay 305 through armature326. The initial circuit of relay 305 is opened at ofi'- normal contacts321 as soon as the switch moves olf normal. At the end of the verticalmovement of the switch, relay 311 falls back and opens the lockingcircuit of relay 305 at armature 348, whereupon relay 305 falls back andshifts the operating conductor 313 from in connection with verticalmagnet 325 into connection with rotary magnet 360. At armature 329,relay 305 closes a circuit including off-normal contacts 335 and thestart conductor 375 for operating the code generator, Fig. 4, in amanner to be hereinafter explained.

When the subscriber dials the next digit 1 in the desired. number, oneinterruption is produced in the circuit of line relay 306 of theconnector C4, and this relay falls back momentarily, momentarilyshunting relay 307 with series relay 311. This operation transmits animpulse of current through armature 334, operated, and over theoperating conductor 313 to rotary magnet 360, through the normallyclosed contacts controlled by armatures 328 and 355. Rotary magnet 360responds to thisimpulse of current and rotates the wipers 357-359 onestep into engagement with the terminals of the called line. Relay 311 is`energized in series with the rotary magnet. At armature 347, relay 311disconnects test wiper 358 from the upper winding of relay 312 andconnects it instead through armature 350 to busy relay 310, and atarmature 348 disconnects ground trom armature 344 so as to prevent thepremature shunting of relay 311 in case relay 310 energizes during therotary movement due to the passing of wiper 358 over busy test contacts.

The operation taking place at the end of the rotary movement depends uon whether the called line is busy or idle. f the called line is busy,relay 310 is energized through test wiper 358 when the wipers come torest on the contacts of the called line, and, when relay 311 falls backat the end of the rotary movement, a locking circuit is completed forbusy relay 310 from the grounded releasetrunk conductor 302 througharmature 342, operated, normally closed contacts controlled by arma-ture347, and armature 350. Relay 311 is shunted at armature 348, normal,through armature 344, so as to prevent it from operating subsequentlyand interfering with the circuit of busy relay 310 in case the wallingsubscriber should again turn his calling device before hanging up hisreceiver.

In order to inform the calling subscriber of the busy condition of theline, busy relay 310 at armature 346 connects the busy lead, coming fromthe busy tone transformer 377, to the lower talking conductor throu harma ture 356. When the calling subscri er hears the tone produced bythe busy tone machine, he is expected to hang up his receiver and bringabout the release of 4the operated switches.

Assuming now that the desired line is idle of the lineswitch LS2 tobattery. This cutolf relay of the lineswitch LS2 operates over thiscircuit and disconnects the associated line relay from the conductors ofthe called line. The cut-off relay of the lineswitch on the called linecorresponds to the bridgecut-off armature 116 of the lineswitch LS1 andthe winding 115. The cut-off armature of the called lineswitch isoperated, but thel pull down armature is not operated owing to therelatively weak pull of the bridgecut-off winding.

In the connector C4, relay 312 operates in series with the cut-offwinding of the called lineswitch and closes a locking circuit for itslower windin at armature 352 including a branch of the ocking conductor314. At armature 354, rela 313 prepares a new locking circuit for re ay305; at armature 353 it prepares a circuitfor pick-up relay 308; atarmature 350 `it opens a point in the previously traced circuit of busyrelay 310 so as to prevent this relay from o erating over a similarcircuit when the last dlgit is dialed; at armature 351, it places aground potential on test wiper 358 independent of the ground potentialpreviously placed on this Wiper through the test winding of the relay;at armature 355 it connects the operating magnet 373 of the codeselector C84 to the operating conductor, at the same time disconnectingrotary magnet 360; and at armatures 349 and 356 it connects up theWipers 3 57 and 359.

When the next and last digit, the code selecting digit 5, is dialed,line relay 306 falls back five times, and shunts relay 307 with relay311 five times, thereby transmitting tive impulses of current overconductor 313 to operating magnet 373 of the code selector CS4. Magnet373 responds to the five impulses of current and advances the wiper 374into engagement with the fifth associated bank contact. Relay 311 isenergized throughout this series of impulses also, and, when it fallsback at the end ofthe series, it closes at armature 348 a circuit forbusy relay 310 through ofi-normal contacts 372 of the code selector CS4.Relay 310 operates at this time and, in effect, locks itself energizedat armature 344 by closingl a shunt around relay 311'including armature348, normal. It will be noted that the busy tone circuit is not closedat this time owing to the fact that arnature 356 of switching relay 312is operate The connection has now been extended to the desired line andthe code selector CS4 has been set on the ringing-code conductorcorresponding to the code necessary to signal the subscriber at thecalled substation. In order to insure that the ringing of the calledsubscriber will begin only at the beginning of a code, the pick-up relay308 has been provided to close the circuit of the ringing relay 309 onlafter a pick-up impulse has been receive over pic -up conductor 376 andthrough the operated armatures 343 and 353.' The code generating deviceshown in Fig. 4 grounds the pick-up conductor and the rin 'ng-codeconductors at the proper time as wil be exlained hereinafter. At thispoint it will su ce to say that a pick-up impulse is shortly receivedover impulse conductor 376, whereupon pick-up relay 308 operates andlocks itself to conductor 314 at armature 337, at the same time openingits initial energizing circuit. At armature 338, relay' 308 completes aconnection from ringing relay 309 to the wiper 374 through armature 327.Accordingly, ringing relay 309 operates each time an impulse is placedon ringing code conductor 5, in a manner to be subsequently explained.Eachtime it operates, it laces ground on the lower wiper 359 and 1tplaces ringing current on the upper wiper 357, operating the bridgedringers at the party-line substations. The ringing code sent out is, ofcourse, that of the substation T2 and the subscribers at the othersubstation do not respond.

When the subscriber at substation T2 responds to the ringin of his bellby removing his receiver, a circuit is closed through the two coils ofthe ringer in parallel for the supervisory relay 304. This circuit, itwill be noted, includes wipers 357 and 359, armatures 349 and 356,armatures 339 and 340, and the right-hand repeating-coil windings. Relay304 operates when its circuit is closed and closes at armature 322 acircuit for reoperating relay 305. Relay 305 closes a locking circuitfor itself at armature 326 including armature 354; it disconnectsringing relay 309 at armature 327; and at armature 329 it renizovesground from the starting conductor 3 5.

It will be noted that the resistance 324 is inserted into the circuit ofline relay 306 at armature 323 of relay 304. This operation is of noparticular utilityat this time, but is performed in order to ive acalling operator supervision in case tie connection is set u through anoperators switchboard, as will Ee explained hereinafter.

The two subscribers may now converse with each other, the heavy linesbeing used to outline the talkin circuit. It is understood, of course,that a ocal source of talking current supply is used in both cases.

Release of connection from T1 to T2 ance 324 so as to give the callingoperator disconnect supervision in case lan operator is handling theconnection.

When the subscriber at substation T1 han up his receiver `relay 201 ofthe repeater l falls back and opens at armature 204 the circuit of rela306 of the connector C4. Relay 306 falls ack and shunts relay 307 withseries relay 311, but relay 311 does not operate at this time because 1tis shunted in turn through armature 348, normal, and armature 344. Atthis time, the circuit ofrelease relay 307 includes armature 334,operated, armature 328, and the vertical magnet 325. As a -result,vertical magnet 325 operates when the release relay 307 is shunted, butthe shaft and wipers are not disturbed due to the usual mechanicalconstruction'of the switch which prevents further elevation of the shaftand wipers after they have been rotated. Shortly afterit is shuntedrelay 307 falls back and opens the circuit of vertical magnet 325 atarmature 334, at the same time closing a circuit through off-normalcontacts 336 for release magnet 330 and a branch circuit through thearmature 341 for release magnet 371 of the code selector. Releasemagnets 330 and 371 now operate to start the restoration of theirrespective switches to their normal positions. In addition, relay 307removes ground from release trunk conductor 302 at armature 332 and atarmature 333 it removes ground from the locking conductor 314.Responsive to the removal of ground from release trunk conductor 302 theselector S4, Fig. 2, releases in the usual manner. When ground isremoved from the locking conductor 314, relays 308 and 312 fall back.The falling back of relay 312 is retarded sli htly by the. cop er on itsarmature end. When relay 312 alls back it replaces the ground potentialon conductor 302 after a sucient time has ela sed to permit the releaseof the selector S4 ig. 2, to be started by the falling back of theswitching relay (not shown) of the selector. The circiut path throughwhich the ground potential is replaced includes armature 348, normal,oil-normal contacts 372 of the code switch, amature 350, normally closedcontacts controlled by armaturev 347, and armature 342. This pathbetween ground and the release trunk conductor 302 is established so asto render the connector and the code switch busy while they arereleasing.

Assuming that the code selector CS4 reaches its normal position beforethe connector C4 reaches its normal position, as will usually be thecase, the circuit of relay 310 and the path throughwhich ground issupplied to release trunk conductor 302 is opened at off-normal contacts372 when the code selector reaches its normal position. Relay 310thereupon fallsback and opens the circuit of magnet 371 at armature 341,and at armature 344 removes the shunt from around the Winding of seriesrelay 311, whereupon relay 311 o erates in series with release magnet330 an at armature 348 applies ground to release trunk conductor 302through armature 326, normal. This second guarding circuit isestablished to guard the connector from seizure during its release.

When the shaft of the connector C4 reaches its normal position,off-normal contacts 335 and 336 o en, and olf-normal contacts 321 close.Tie circuit of the release magnet and the series relay is opened at srings 336, and the circuit of relay 305 iuc uding conductor 302, nowgrounded by series relay 311, is reestablished, .and relay 305 operates.Relay 311, however, falls bacl: an instant later and removes ground fromconductor 302, rendering the connector idle again and releasing relay305 In the repeater R1, Fig. 2, when line relay 201 falls back, asabove-mentioned, it o ens the circuit of the release relay 202 and paces the said relay 202 in a closed circuit with the result that relay202 falls back after a slight interval, removing ground from releasetrunk conductor 157 and opening the circuit of relay 203. The switchingrelay 135 of the selector S1 and the magnet of the lineswitch LS1 bothdeenergize, and relay 135 at armature 150 closes a circuit for releasemagnet 146 at armature 150 and through armature 144 and off-normalcontacts 143. This circuit includes series relay 133. Relay 133 andmagnet 146 both operate, and relay 133 closes a circuit for steppingrelay 134 through the rotary-magnet interrupter contacts and olf-normalcontacts 141. Relay 134 now operates and applies ground potential againto release trunk conductor 125 so as to prevent the master switch fromagain stopping opposite this selector until it is fully released. Whenthe normal position is reached, the release magnet and series relaycircuit is opened at contacts 143; and the circuit of relay 134 isopened at contacts 141. Relay 134 thereupon falls back and removesground from the release trunk conductor, and relay 133 falls backshortly thereafter.

All trunks busy at selector S1 Consider now the case when the selectorS1 is operated, but is unable to find an idle trunk. The rotary movementtakes place in the hereinbei'ore described manner and continues untilthe wipers 153--155k pass oi the last bank contact upon the eleventhrotary set. When this occurs, springs 136 and 142 are operated by theusual cam arrangement. The circuit of relay 135 is opened at springs 142to prevent this relay from operating at this time. At spring 136, thecommon busy tone lead is connected to the lower talking conductor 126,so as to give the calling subscriber a busy tone. Upon hearing thistone,`

the calling subscriber is expected to hang up hls receiver and bringabout the release of `.the connection.

Operation of code-generating device ate the impulses to operate theother relays.

The remaining relays, especiall relays 405- 410, operate to count theimpu ses generated by relays 403 and 404, and the device as a wholels'eapable of assuming any one of nineteen posltlons, successively, theoperation be- 1ng repeated in cycles. The positions of the devlce 1nwhich the various relays are operated have been noted on the drawings.Also, the pos1tions of the device in which the principal conductors aregrounded have been note 1n order that the disclosure may be understoodbetter.

When start conductor 37 5 is grounded, ground 1s extended through thelower armature of relay 402 to conductor 416, closing a c1rcu1t forrelays 403 and 404, in series, through the resistance element 422. Relay404 belng short circuited, rela Y403 is the only one that respondsimmediatelly. When relay 403 operates, it places ground on conductor 417at lts upper armature, and removes the shunt from around relay 404 atits lower armature. Relay 404 operates and prepares to place ground onconductor 419, and at the same time shunts relay 403. Relay 403 fallsback, and the device may be said to be in its second position. Inthesecond position of the device, a circuit is closed through the upperarmatures of relays 403 and 404 for the upper winding of relay 406,including conductor 419 and the upper armature, normal, of relay 406.Relay 405 operates and closes a locking circuit for itself at its upperarmature including the upper windingof relay 405, the lower armature ofthe said relay, and the grounded conductor 416.

With the device in position two, relay 404 is short circuited at thelower armature of relay 403, and relay 404 shortly falls back, thedevice thereupon passing into position three. When relay 404 falls back,it removes ground from conductor 419, whereupon relay 405 operates inthe locking circuit of relay 406, and at its upper armature prepares acircuit for shunting relay 406. It will be noted now that a new lockingcircuit is completed for relays 405 and 406 in series, and that thecircuit of the upper windings of these relays is opened. The new circuitincludes the lower windings of the relays in series and the inner lowerarmatures of the two relays.

When relay 404 alls back it removes the shunt from around relay 403 withthe result that relay 403 operates again and removes the shunt fromaround relay 404. Relay 404 now reoperates and shunts relay 403. This oeration of relays 403 and 404 continues, 1n t e manner described, untilit is terminated bv the action of relay 402, as will be desdribedhereinafter.

It will be noted, that relay 403 is labeled 1, 3, 5, etc. while relay404 is labeled 1-2, 3-4, etc. These labels indicate that relay 403 isoperated in positions 1, 3, 5, etc., and that relay 404 is operated inpositions 1 and 2, is released momentarily, is operated again inpositions 3 and 4, etc.

Vith the device in position 4, ground is again placed on conductor 419,short circuitin lower winding of relay 406. Relay 406 fa ls back whenthis takes place and opens the previously established locking circuit atits inner lower armature. Relay 405 remains operated over conductor 419.

When the device arrives in position 5, ground is removed from conductor419, whereupon, relay 405 falls back.

The above described operation of relays 405 and 406 is repeated,begininng with position 6.

While rela 406 is operated in positions 2 and 3, groun from conductor416 is held on impulse conductor 420, extendingto the similar relays 407and 408. The result is an operation of relays 407 and 408 similar to theabove described operation of relays 405 and 406, but the time requiredfor a complete operation is twice as long as that of relays 405 and 406,on account of the fact that only half as many impulses are deliveredover conductor 420 as are delivered over conductor 419. It may be seen,therefore, that relay 408 is operated in positions 2 5, 10-13, and 18,and that relay 407 is operatedI in positions 4-7, and 12-15.

It will be noted, that round from conductor 416 is placed on contgluctor421 as long as relay 407 is operated. The result is that conductor 421is grounded in the positions of the device in which relay 407 isoperated, conductor 421 being the impulse conductor extendin to thethird pair of counting relays 409 ancgl 410. Itmay be seen, therefore,that relay 410 is operated in positions 4--11, and that relay 409 isoperated in positions 8-15.

When 418 is rounded in position V2, a circuit is closed t rough thelower armature of relay 412 for relay 413. Relay 413 operates and locksitself through the middle lower y armature of relay 412 to conductor416, and remains operated until relay 412 o erates in position 13, aswill be pointed out ereinafter.

When the device arrives in position 6, relay 414 is operated from thegrounded conductor 416 through the inner lower armature of rela-y 407,lower armature .of relay 406, and the lower armature of relay 413. Relay414 operates and locks itself through the locking conductor of relay413, with the result inner lower armature of relay 405, inner lowerarmature, normal, of relay 406, middle upper amature of relay 408, andthe middle upper armature of relay 409. At its lower armature relay 411locks itself and relay 401 to conductor 416. Relay 401 prepares a lockincircuit for relay 402 at its inner amature.

hen the device arrives. in-position 13, relay 405 falls back and closesat its lower armature a circuit through the inner up r armature of rela411 for relay 412. Re ay 412 operates an locks itself to conductor 416until conductor 416 is ungrounded in position 18. At its middle lowerarmature, relay 412 opens the locking circuit of relays 13kand 414,whereupon these relays fall When the device arrives in position 18,relay 408 is operated again, and it completes at its upper armature acircuit for relay 402 including the upper armature of relay 412'and themiddle lower armature of relay 409. Relay 402, thereu on operates andlocks itself to conductor 3I75 through the inner armature of relay 401,at the same time opening its initial circuit. At its lower armature,relay 402 removes ground from conductor 416 and y laces ground onpick-up conductor 376. he removal of ground from conductor 416 stops theoperatlon of relays 403 and 404 and permits the operated relay 404 tofall back, and it opens the locking circuits of the relays 405-414,permitting such of these relays as are operated to fall back. Relay 401,which is in series with relay 411, is slow-acting and does not fall backright away when its circuit is opened upon the removal of ground fromconductor 416.

When relay 401 falls back it opens'the locking circuit of relay 402, thedevice is in osition 19. A moment later relay 402 falls ack,

and removes ground from pick-up conductor 376, reapplying it toconductor 416; then the device is 1n position 1 again.

The above described operation is repeated over and over as lon as theound potential remains on start con uctor 375.

Considering now how the codes are placed on the various conductors, theconductor extending to terminal 1 is grounded through the lowerarmatures of relays 401 and 408 while the device is in positions 2-5;this code corresponds to one long ring.

The conductor extending to terminal 2 i's grounded through the upperarmatures of rea s 403 and 411, and the middle armature of re ay 410while the device is in positions 1 rand 3; t is code corresponds to twoshort rings.

Thel conductor extending to terminal 3 is grounded in positions 3, 5,and 7 of the device through l.the upper armatures of relays411, 413, and409; this code corresponds to three short rings.

The conductor extending to terminal 4 is connected to the impulseconductor 417 through the upper armature of relay 411 and the middleupper armature of relay 410, and is grounded in positions 5, 7, 9, and11; this code corresponds to four short rings.

In a similar way the rcm'ainin code conductors are grounded in thepositions indicated. The code laced on the conductor extending totermmal 5 corresponds to five short rings; the code placed on conductor`6 corresponds to two long rings; the code placed on conductor 7correspondsl to three ong rings; the code placed on conductor 8corresponds to a short ring and a long ring; the code placed onconductor 9 corresponds to a short ring and two long rings; and the codelaced on` conductor 10 corresponds to two siiort rings and two longrings.

@all from substation T1 to substation T4 It will now be assumed that thesubscriber at substation T1, Fig. 1, desires to converse with thesubscriber at substation T4, Fig. 7. In order to complete theconnection, the subscriber at substation T1 dials the number assigned tothe manual exchange C (the digit 4). It will be assumed, that when thesubscriber removes his receiver the lineswitch LS1 seizes the selectorS1, and that when the'digit 4 is dialed the selector S1, uponI raisingits Wipers to the fourth level, rotates Ithem and finds the trunk linecomprising conductors 159-161, extending to the trunk circuit TG1, asthe iirst idle trunk line. When this occurs, `line relay 223 of thetrunk circuit TCl operates over the calling line and places ground onthe release trunk conducnection including armature 225 between theringing relay 222 and the 1 ringing code conductor of the code eneratingdevice in exchange A. The code aced on this conductor 'corresponds toone ong ring, and it 1s, of course, repeated at' intervals. At armature230, ground is placed on conductox 375 through armature 224 so as tostart the asso- 'ciated code-generating device.

Each time ground is placed on the'rin 'ingvcode 'conductor -connected totermina 1,` ringing'relay 222 operatesand pro]ects ringingfc'rrent outE"over the trunk line TL1.

This ringing current passes through the lefthand windings of therepeating coil associated with the trunk circuit TG3, Fig. 5, to theupper windin of the ring-u relay 501. Relay 501 respon s and closes allocking circuit for itself through'its lower winding at armature `506,including armature 514 of sleeve relay'505. At armature 507, relay 501closes a circuit for the line lamp 515.

When the operator notes the lighted condition of the lamp 515, sheinserts the answering plu'g of an idle cord circuit, such as the cordcircuit CC, into the jack J2. When the plug has been fully inserted, acircuit is closed from the exchange battery through 'the two left-handwindings of the cord circuit CC for the relay 504 in the trunk circuitTG3 including the right-hand windings of the repeating coil in the trunkcircuit TG3, and armatures 508 and 510. At armature 511, relay 504places ground on the lowei` terminal of the sleeve relay' 505, whereuponsleeve relay 505 operates over the sleeve conductor of theleft-handjplug of the cord circuit and'closes a lockingv circuit foritself at armature 514, at the sa'me time opening the locking circuit ofrelay 501. Relay 501 falls back and extinguishes the lamp 515. At

armature 512, relay 505 shunts the condenser "95 in the left-handwindings of the repeating coil so as to improve the talking conditions,and at armature 513, it connects ground throu h relay 502 to both innerterminals of the le -hand repeating coil windings, thereby closing acircuit over the two conductors lof the trunk line TL1, and the riht-hand windings of the repeating coil at t e trunk circuit TG1 forrelay 221. Relay 221 operates over this circuit and closes a lockingcircuit for itself at armature 224, at the same time removing groundfrom conductor ,375 and disconnecting the code conductor I2 from'theringing relay 222. The closure of the locking circuit for relay 221shunts the current away from supervisory relay 502 in the trunk circuitTO3, permitting this relay to remain non-operated. i

In the cord circuit CC, supervisory relay 516 operates in series withrelay 504 of TG3,

and shunts the associated supervisory lamp so as to keep it A:fromlighting in the sleeve circuit. p

The operator now throws her key K2 into listening A osition andconverses with the calling su scriber. Upon learning that the callingsubscriber desires connection with the subscriber at substation T4, Fig.7, the operator makes a note of the number of the calling substation andthe number of the called substation. She then inserts the right-handplug of the cord circuit CC into the jack 'of an idle trunk line, suchas the trunk line TL4,-extending toexchange D. When the l plug-is to.the jack J3, a circuit is windings of the repeating coil in the ltrunkcircuit and at armature 608 and 610. Relay 604 operates and grounds thelower terminal of relay 605, whereupon relay 605 operates over thesleeve circuit and closes a locking circuit for itself at armature 614.At

armature 612, relay 605 shunts the condenser associated with theright-hand repeating coil windings of the trunk circuit, and at armature613 it connects ground to the two inner terminals of the associated right-hand repeating coil windings, closing a circuit including re ay 602,the two conductors of the trunk line TL4 in multiple, and the line relayof the lineswitch LSB. Relay 602 o erates in this circuit and opens thecircuit o relay 604 at armature 608. Relay 504 falls back and relay 517of the cord circuit CC remains nonoperated, permitting the associatedsuperv isory lamp to become lighted in the sleeve circuit. l p

The lineswitch LS3 now operates and extends the connection to theconnector C5.

, Line relay 803 of the connector C5, now operates over conductors 616and 618 in multiple and closes a circuit for release relay 804. Thecircuit of release relay 804 includes, at this time, the normally closedcontacts controlled by armatures 819 and 857, and rotary magnet 855.Relay 804 upon operating, locks itself to the operating conductor 822 atarmature 826; grounds the locking conduc` tor 701 at armature 825; andat armature 824 placesground on release trunk conductor 617 to maintainthe connector busy to the lineswitches having access to it, and to holdthe lineswitch LS3 operated. When ground is placed on conductor 617,relay 802 operates through off-normal contacts 812 and prepares alocking circuit for itself at armature 817.

p At armature 819 it substitutes vertical magnet 816 for rotary magnet855.

After inserting the right-hand lug of the cord circuit CC into the jackJ 3, the operator inserts the plug of the dial cord DC into the dlal.jack DJ 2. When the operator turns the calling device CD, in accordancewith the first digit 3 in the number of the called substation, theoff-normal springs of the 'calling device CD close a circuit for relay603, whereupon relay 603 opens at armature 610 a further point in thecircuit of supervisory` relay 604, and at armature 609 it disconnectsrelay 602 and substitutes the impulse springs of t e calling device CD.Upon the return of the dial to its normal position, three interruptionsare produced inthe circuit of line relay 803, Fig. 7, and when thenormal position is reached, the off-normal springs bring about thedeener ization of relay 603, whereupon relay 602 1s brought into thecircuit again.

Each time line relay 803 of the connector C5 falls back it shuntsrelease relay 804,

thereby operating vertical magnet 816 three times. Series relay 809, incuded in the shunt circuit around relay 804, operates upon the firstimpulse and, being slow-acting, remains operated throughout the seriesof impulses. At armature 843, relay 809 completes the locking circuit ofrelay 802 so as to maintain the relay o erated after its initial circuitis opened at o -normal contacts 812.

At the end of the vertical movement of the connector, relay 809 fallsback and permits relay 802 to deenergize and transfer the operatingconductor 822 to the rotary magnet 855.

When the calling o erator dials the next digit 0, line relay 803 allsback and operates rotary magnet 855 ten times. Relay 809 is againoperated throughout the series of impulses and it closes at armature 842a circuit for relay 810. Relay 810 operates and at armature 845 connectstest wiper 857 to bus relay 808 through the normally-closed o normalcontacts of the code selector US5. In case the called line is busy,relay 808 is o rated at the end of the rotary movement, w en the wipers856-859 are on the cont-acts of the called line, and the busy tone istransmitted back to the operator at armature 841, in the usual manner.If the line is idle, a circuit for the upper winding of the switchingrelay 811 is completed upon the falling back of relays 809 and 810,which circuit includes the grounded release trunk conductor 617,armature 836, upper winding of relay 811, armature 845, armature 847,test wiper 857, test contact of the called line, and the bridgecutoffwindin (not shown) of the lineswitch LS4. elay 811, upon operating,locks itself to conductor 701 at armature 848; at armature 847 shiftsthe test wiper 857 from the upper winding of relay 811 to ground;connects up the wipers and opens a point in the busy signalling circuitat armatures 846 and 853; shifts the operating circuit to the operatingmagnet of the code selector at ar armature 851; and at armature 850prepares a circuit for pick-up relay 805.

When the calling operator dials the next and lastf digit 5, fiveimpulses of current are transmitted to the operating magnet of the codeselector, whereupon the wiper of the code selector is driven intoengagement with the fifth associated bank contact. Relays 809 and 810are energized throughout this digit, and the circuit of relay 808 ismaintained open at armature 845. When relay 809 falls back, a circuit isclosed at armature 842 through the normally-open off-normal contacts ofthe switch CS5 and for the busy relay 808. Relay 808 operates at thistime and, at armature 837, shunts the series relay 809 so as to preventany further operation of this relay; at armature 839, it shifts theoperating conductor back to vertical magnet 816; it prepares the releasecircuit at armature 835; and at armature 838V it completes theconnection between the pickup conductor and pick-up relay 805. The startconductor 375 havingbeen grounded through contacts 823 and armature 820,the associated code generating device is operating, and, when thepick-up conductor is grounded, pick-up relay 805 operates and locksitself to conductor 701. At armature 829, it completes a connectionthrough armature 818 between ringing relay 806 and the wiper of the codeselector. The ringin current is now projected out over the cal ed line brela 806 in 'xccordance with the code of t e su tation When thesubscriber at substation T4 responds a circuit is closed over the twosides of the called line in parallel for relay 801. At armature 813,relay 801 closes a circuit for relay 802. Relay 802 operates and atarmature 817 closes a locking circuit for itself including armature 849;it disconnects the ringing relay atarmature 818; and at armature 820 itremoves ground from start conduct'or 375. Relay 801,. at armature 814,inserts the resistance 815 into the circuit of line relay 803,'whereuponthe marginall supervisory relay 602, Fig. 6, falls back-and againcompletes a circuit through relay 604, whereupon the right-handsupervisory relay 517 of thc cord circuit CC operates and extinguishesthe associated supervisory 1am so as to give the operator answeredsupervlsion.

The two subscribers may now converse with each other in any desiredmanner, and when the conversation is terminated they both replace theirreceivers.

When the receiver is replaced at the calling substation, line relay 223.of the trunk circuit TCl, Fig. 2, falls'back and removes ground atarmature 229 from release trunk conductor 160, permitting theline-switch and selector, Fig. 1, to release. At armatures 228 and 232the conductors of the trunk line TL1 are switched back to the selectorS2, and

at armature 230 the lockin circuit of relay 221 is opened, whereupon reay 221 falls back.

The supervisory relay 502, Fig. 5, now operates over the trunk line TL1in series with the line relay (not shown) of the selector S2, and atarmature 508 opens the circuit of supervisory relay 516, whereuponsupervisory relay 516 falls back and permits the associated lamp tobecome lighted as a disconnect signal.

The selector S2, see Fig. 8, is incidentally prepared for operation whenits line relay operates over the trunk line in series with thesupervisory relay 502, Fig. 5,

When the receiver is replaced at the called substation, relay 801 fallsback and at armature 814 shunts the resistance 815, whereupon relay 602,Fig. 6, operates again over the trunk line TL4 and gives the operator avflufther disconnect signal by opening the circuit I of supervisoryrelay 517 at armature 608.

Upon perceiving the two disconnect signals, the operator pulls down theconnection.

lVhen the plug is removed from the jack J2,

the associated supervisory lamp becomes ex- J3, sleeve relay 605,*fallsback and removes ground from the'inner terminals .of the associatedright-hand repeating coil windin s, whereupon line relay 803 of theconnector falls back and shunts release relay 804, causing an incidentaloperation of vertical magnet 816. After a slight interval, relay 804falls back and, at armature 824, removes ground fromv conductor 617 soas to permit the lineswitch LSB to release. At armature 825 `it removesground from conductor 701,

permitting relays 805 and 811 to fallback. The relay 811 releases thebridge-cut-o winding of the lineswitch LS4 at armature 847, and atarmature 849 opens the locking circuit of relay 802,I whereupon relay802 falls back. Release magnet 821 operates through oil-normal contacts827, and the release magnet of the code selector operates throughoff-normal contacts 835.' It is to be noted, that no reapplication ofground application of ground potential to conductor 617 occurs at thistime, as it is not desired to busy the connector C5 during the release.When the code selector CS5 reaches its normal position, the circuit ofrelay 808 is o ened, and relay 808- falls back, opening the re easemagnet circuit of thecode selector at armature 835. At armature 837,relay 808 removes the shunt from around the winding of relay 809,whereupon relays 809 and 810 operate agaln. However, the reapplicaticnof ground to the release trunk conductor, described in connection withthe similar relay 311 of the connector C4, does not occur at this time,owing to the elimination of the connection at armature 817 correspondingto the connection between the resting contact of armature 326, Fig. 3,and the release trunk conductor 302.

`When the connector C5 reaches its normal position, the circuit ofmagnet 821 and relay 809 is opened at off-normal contacts 827. Relay 809now falls back and opens the circuit of relay 810 at armature 842, withthe result that .relay 810 falls back also.

The entire connection is now released, and the apparatus involvedtherein may be used in setting up other connections.

Regarding the reason for the elimination of the busy-during-releasefeature from the connector C5, it may be pointed out that, in case the'connector Q5 er the code Selector US5 lool should become mechanicallydefective so that no release would occur, the ground potential wouldremain applied to conductor 617, with the result that, in case thelineswitch used to 4make the original call should be reo rated rightaway to make a new call be ore the master switch has picked-up the line'they are releasing. On the other-hand, theV busy-during-release featurehas been applied to the connector C4, Fig. 3, because this connector ispreceded by a selector and as soon as the release starts the selector isfreed and thereis no danger of a line being locked out of commissionupon the reapplication of the ground potential to the release trunk.However, notwithstanding the danger of lines bcing locked out ofcommission, the guard-durfing-release feature has been applied to theselector S1, as it is assumed that an vattendant is present most of thetime in exchange A, and that he will be ready to take care of suchsituations as they occur. to exchange B.

@all from substation T4 to substation T3 In order that the automaticrota-ry operation of the connector C5, Fig. 7, be understood, thisoperation will be ex lained in connection with a call from the suscriber at substation T4 in exchange D, to the sub- A scriber atsubstation T3 in exchange C.

It will be assumed that, when the subscriber at substation T4 removeshis receiver, the lineswitch LS4, Fi 8, seizes the connector C5 at amultiple o the conductor 616-618, see Figs. 6 and 7. When this occurs,the connector C5 is prepared for operation in the manner hereinbeforeexplained, and a holding circuit for the calling lineswitch is closedover conductor 617.

The calling subscriber now dials the number 211 assigned to the exchangeC for the use of subscribers in exchange D. When the digit 2 is dialed,the connector C5 responds by raising its Wipers opposite the secondlevel of bank contacts.

When the second digit, the digit 1, is dialed, the wipers of theconnector C5 are rotated one step in the hereinbefore described manner.It Will be recalled that the series relay 809 is operated in series withthe operating conductor 822 when the rotary movement of the connectortakes place, and that relay 810 is operated by relay 809 at armature842. The operation taking place at the lend, of the- The same appliesdirected rotary movement of the connector, depends u on whether thetrunk line '1`Llis busy or id e, itibeing assumed that the trunk 'l`L4is the one terminating in the first set of bank contacts in the secondlevel. Assuming that the trunk line is busy, there is agroundpotentialon the test contact thereof, nowencountered by test wiper857, and a circuit is therefore closed through armatures 847and 845, andoil-normal contacts of the code selector CS5 for busy relay 808. Busyrelay 808, at armature 840, prepares a circuit for stepping relay 807,including the rotary test wiper 858. When series relay 809 falls backand opens the circuit of the slowacting relay 810 at armature 842, itcompletes at armature 844 a connection between relay 807 and the testwiper 858, this connection including the interrupter contacts 854 andarmature 852. Relay 807 now` operates from the ground potential on thetest conductor of the trunk line, which ground potential is carried tothe rotary test contact through th'e associated jumper connection. Uponoperating, relay 807, at armature 833, closes a holding circuit forslow-acting relay 810, so as to prevent it from falling back at thistime. At armature 834, relay 807 locks itself to the release trunkconductor 617 by placing ground therefrom on the test wiper 858, and atarmature 832 it closes a circuit over the operating conductor 822 forrotary magnet 855. Rotary magnet 855 now ,responds and ad vances the wiers another step. Near the end of its stro e, magnet 855 opens thecircuit of relay 807 at contacts 854, whereupon relay 807 falls back ando ens the rotary magnet circuitresulting in t e deenergization of therotary magnet. If the test contact of the second trunk line is busy, thestepping relay operates again and the rotary movelnent continues. Vhenan idle trunk line is reached, relay 807 ceases to operate and the busyrelay 808 falls back. As an alternative, the wipers may be driven to thelast trunk line of the group, and, if this trunk line is busy. the busyrelay remains operated, but no `further operation of the stepping relay807 takes place on account of the ommission of the corresponding umperconnection between the rcgular test contact and the rotary test contactof the last trunk line. The busy signal is transmitted back in thelatter instance, and the calling subscriber replaces his receiver, bringing about'the release of the connection.

For the purpose of the present description it will be assumed that thetrunk lineTL4 is idle when tested, With the result that relay 807 doesnot operate,and busy relay 808 remains normal when the directed rotarymovement is completed.

Responsive to the deenergization of relay 810, which takes place whenits circuit is opened by relay 809, the switching relay 811 operates inseries with the bridge-Cutoff

